As a result of an increasing trend towards the adoption of renewable energy sources, the installation of solar panels, and in particular arrays of photo-voltaic (PV) panels, is gaining in popularity, not only for industrial and institutional applications, but also in the domestic and rural environments. Whether for the industrial, institutional, domestic or rural environment, the solar panels are often mounted on the rooftops of buildings—most typically in the area where the solar energy is required. Roof structures are particularly convenient for this purpose as they present a large surface area directed towards the sun and are often largely out of view from the normal visual perspective, thereby rendering the installations relatively unobtrusive. Generally horizontal or flat rooftops are particularly convenient for this purpose as they provide an even and stable working environment for the assembly, installation and maintenance of a solar panel array. In this connection, it will be noted that even “flat” or substantially horizontal rooftops will often have a slight grade or slope from a few degrees up to about 10° to promote rainwater drainage.
In many cases, horizontal or flat rooftops have a sealing layer as an outer covering and this sealing layer is typically formed by a flexible membrane of a rubber-based or polymer material, sometimes including bituminous or tar-based compounds. In particular, the sealing layer or “skin” of flat rooftops is often formed by one or more sheets of a flexible material selected from the group including thermoplastic poly-olefins (TPOs) or flexible polyolefins, flexible polyolefin alloys (FPA), ethylene-propylene-diene M-class rubber (EPDM), poly-vinylchloride (PVC) and polymer-bitumen sheeting. Some of these materials have been in use in roofing structures since the 1960's and, as such, are commonly found on the rooftops of existing buildings today.
Such rooftops present particular problems in the mounting of solar panel arrays because it is especially important to ensure that the outer sealing layer or membrane of the rooftop remains intact and that no, or only minimal, perforation or penetration of the sealing layer occurs. In this regard, the flexible outer layer or membrane serves to ensure a seal against the ingress of water into the roof structure. Accordingly, every time the outer sealing layer or membrane sustains a perforation or puncture, the waterproof properties of the membrane are compromised and a potential source of rainwater leakage or seepage into the roof is created.
One of the known techniques for mounting of solar panel arrays on such flat rooftop surfaces includes the use of elongate bearing rails as the basic carrier elements for the solar panel array. The bearing rails typically have a constant profile or cross-section (typically provided as a so-called a “cap”-section or “hat”-section) and have conventionally been fastened or secured on the sealed outer surface of the rooftop in a number of different ways, including being held down with weights or ballast, bolts and screw fasteners, adhesive and solvent bonding, and cold or hot fusion or welding. These techniques have disadvantages, however.
The use of weights or ballast, for example, is not suitable for all rooftops because it can substantially increase the loading on the roof structure and many rooftops are simply not designed to carry substantially increased static loads, particularly in view of the fact that wind forces will additionally load the structure. Furthermore, the transportation of large amounts of ballast can also be cumbersome. Moreover, mounting systems using weights or ballast as main fixation means are frequently of tub-like shape associated with large material consumption resulting in inadequate material and transportation costs. Furthermore, such structures cover a large area of the roof, which is often not desirable because this hinders the free drainage of water on the roof.
Bolts and screw fasteners, on the other hand, have the disadvantage that they penetrate the roof “skin” or sealing layer, which—as noted above—carries the inherent risk of a possible subsequent seepage or leakage of water into the roof structure. This risk is further heightened in the event that the solar panel array ever needs to be disassembled and removed from the rooftop.
Adhesive bonding and solvent bonding have the disadvantage of relatively low bond durability and can also not be employed for all types of conventional sealing layer or sealing sheet material. On the other hand, the technique discussed in German utility model DE 20 2008 209 134 U1, which describes the use of cold fusion or welding to secure the bearing rails to the roof surface, requires that the bearing rails first be coated with a material that corresponds to the sealing layer (e.g. PVC, TPO, EPDM, etc.), which can be extremely time- and cost-intensive. Furthermore, hot fusion or welding with a heating device in that arrangement can be difficult due to the rigidity of the rails and can lead to irregular bonding and associated failures.
The above fixation techniques can also have the disadvantage that forces generated due to thermal expansion of the solar panel modules arranged on and/or extending between the rail sections, have to be fully absorbed by the join between the rail and the roof sealing layer. With significantly different coefficients of thermal expansion between the roof structure and the solar modules, overloading or even tearing of the sealing layer can result.
In view of the above issues associated with mounting solar panel arrays on rooftops sealed with a polymer or rubber-based sheet layer or membrane, it is an object of the present invention to provide a new and improved mounting system with which one or more of these problems may be overcome or at least minimized. It is also an object of the invention to provide a new and improved support device for use in such a mounting system.